Description and History

NPL Listing History

NPL Status: Final

Proposed Date: 12/30/82

Final Date: 09/08/83

Deleted Date:

The entire area of the Indian Bend Wash Superfund Site (IBW Site) covers approximately 13 square miles in Scottsdale and Tempe, Arizona. EPA divided the Site into two areas known as North Indian Bend Wash (NIBW) and South Indian Bend Wash (SIBW). NIBW and SIBW are on separate cleanup tracks.

This Site Overview focuses on NIBW only. More information on SIBW can be found at: SIBW.

There are numerous industrial facilities located in the NIBW area. Up until the 1970s, before our current environmental regulations existed, industrial solvents containing volatile organic compounds (VOCs) were typically disposed of directly onto the ground or in dry wells. These disposal practices, along with other releases, resulted in the present groundwater contamination at NIBW. At the NIBW Site, the groundwater is present in three separated levels or layers. These layers are referred to as the Upper, Middle, and Lower Aquifers. All three of these aquifers are contaminated.

Groundwater contamination at NIBW was discovered in 1981 when elevated levels of VOCs including trichloroethylene (TCE), tetrachloroethylene (PCE) and chloroform were found in several Scottsdale-area drinking water wells. As a result, local water providers stopped using those wells for drinking water.

EPA and ADEQ have been involved in investigations and cleanup activities at NIBW since the initial discovery of VOCs in the groundwater in 1981. The entire Site, including both NIBW and SIBW, was placed on EPA's National Priorities List (NPL), or Superfund list, in 1983.

Maps

Using groundwater data collected annually, the locations of the NIBW groundwater plume(s) are shown under the Documents and Reports section below.

Contaminants and Risks

Contaminated Media

Groundwater

Soil and Sludges

Groundwater and soils (in certain isolated areas) are contaminated with VOCs, including TCE and PCE.

The primary risk at NIBW was to individuals who may have consumed contaminated groundwater before it was discovered in 1981. Since individuals are currently not drinking the contaminated groundwater, there is no direct human health threat associated with the groundwater contamination. All drinking water in the Scottsdale area is provided by municipal drinking water suppliers. This water can not be served to customers unless it meets all drinking water standards set by the federal Safe Drinking Water Act.

Wells can not be drilled in the state of Arizona without a permit from the Arizona Department of Water Resources (ADWR). EPA works with ADWR to coordinate the cleanup efforts at NIBW. If someone applied for a well permit, ADWR would inform them of the risks of using the groundwater for drinking, showering, etc.

The greatest risk associated with contaminated soil is its potential to impact the groundwater. If individuals were to come into direct contact with contaminated soil, due to the low concentrations of contaminants present in surface and deep soil, the potential health risks would be minimal or insignificant.

The Indian Bend Wash (the Wash) itself runs north/south through NIBW. Historically, the Wash was a natural desert wash emptying into the Salt River. The Wash now consists of a series of linked ponds surrounded by irrigated recreational areas such as parks and golf courses. Groundwater used to be used to fill these ponds and irrigate the recreational areas. After VOCs were detected in the surface water and sediment of some of the ponds in 1984, the City of Scottsdale stopped using groundwater to fill the ponds. By 1988, analysis of surface water and sediment in the ponds demonstrated that contamination was no longer present in these ponds. Since that time, NIBW cleanup efforts have focused on the groundwater and the soil.

If you resided in the NIBW area prior to the well closures in 1981, you may have been exposed to TCE.

If you have questions about TCE, please review the Agency for Toxic Substances and Disease Registry's (ATSDR's) TCE fact sheet at http://www.atsdr.cdc.gov/toxfaqs/TF.asp?id=172&tid=30 and EPA'sTechnical Factsheet on: TRICHLOROETHYLENE (TCE) under the Documents and Reports section below.

In April 2007, the Agency for Toxic Substances and Disease Registry (ATSDR) received a request to conduct a public health evaluation of potential past exposures to contaminants in the municipal drinking water system in the North Indian Bend Wash site that may have occurred before the system’s contaminated wells were closed in 1981. ATSDR is a federal public health agency, part of the U.S. Department of Health and Human Services. ATSDR serves the public by using the best science to respond to public health concerns and provide health information to prevent harmful exposures to toxic substances. ATSDR completed a public health assessment of the site in 1989 in accordance with the Comprehensive Environmental Response, Compensation, and Liability act of 1980, as amended. In September 2008, ATSDR issued a public health consultation that reviewed ATSDR activities and summarized both the toxicological information for TCE exposures and the limited TCE data for the municipal water system for the period of concern. The health consultation is available at http://www.atsdr.cdc.gov/hac/pha/HCPHA.asp?State-AZ If you have a question or need more information, please call (800) CDC-INFO or visit the ATSDR website at http://www.atsdr.cdc.gov/.

Who is Involved

This site is being addressed through a consortium of companies in the area referred to as the NIBW Participating Companies (Motorola, GlaxcoSmithKline and Siemens). Please see the "Potentially Responsible Parties" section below for additional details.

Investigation and Cleanup Activities

This site is being addressed in two long-term remedial phases. For the most part, the work has been divided into the following management units: (1) groundwater; and (2) soil. The EPA is addressing NIBW as a separate area of study from SIBW because the contaminants come from different sources and the groundwater plumes are not contiguous.

Remedy Selected

Groundwater Remedy: In 1988, EPA issued a Record of Decision (1988 ROD) which required containment or capture of the groundwater contamination by extracting groundwater from the middle and lower parts of the aquifer. The remedy also required treatment of the extracted groundwater to drinking water standards. EPA negotiated a Consent Decree with the potentially responsible parties (PRPs) for implementation of this groundwater remedy. The Consent Decree outlined how the PRPs would complete the cleanup work.

To treat the extracted groundwater the Central Groundwater Treatment Facility (CGTF) was constructed and began operation in 1994. The CGTF treats the contaminated groundwater using a technology known as air stripping and provides treated water to the City of Scottsdale which is used as part of their municipal water supply. Groundwater treatment is anticipated to be necessary for approximately 40 more years.

Following construction and initial operation of this remedy it became apparent that the groundwater contamination in the middle and lower parts of the aquifer had not been contained or captured and that the CGTF was not adequately treating the groundwater. As a result, additional actions were taken. These additional actions have become known as the “Remedy Enhancements” and are discussed in more detail below.

Soil Remedy: An investigation of the nature and extent of contamination found in soil and groundwater in the upper aquifer was completed in April 1991. In total, 14 facilities or distinct areas were investigated for soil contamination at NIBW.

In September 1991 EPA issued a Record of Decision (1991 ROD) which required the use of soil vapor extraction (SVE) to clean up contaminated soil (in three specific areas) and continued monitoring of the upper aquifer. SVE was required at Area 7, Area 8 and Area 12 because it was determined that these areas could continue to contaminate the groundwater. In August 1993, EPA completed negotiations for a second Consent Decree with the PRPs for implementing the cleanup actions selected in the 1991 ROD. Soil cleanup using SVE has been completed at Areas 8 and 12. Soil cleanup at Area 7 is expected to be complete in 2004. The groundwater monitoring well network for the upper aquifer has been installed and groundwater sampling is being conducted every six months.

Final Remedy: In November 2000, the PRPs completed a Feasibility Study Addendum (FSA) which evaluated the effectiveness of all the cleanup work that has been completed at NIBW and evaluated cleanup alternatives that would meet all of the cleanup objectives for NIBW. EPA used the information in the FSA to evaluate cleanup alternatives that will combine all of the actions taken and actions that need to be taken into one final cleanup decision. EPA signed a final Record of Decision Amendment in September 2001. The final remedy selected in September 2001 includes the following components: the actions required by the 1988 ROD, the Remedy Enhancements described above become required actions, plus one new extraction well and one new recharge well, continued evaluation of groundwater conditions using the groundwater model and contingency actions for Area 7 and Area 12 groundwater plumes.

In May 2002, EPA, the State, the PRPs and the City of Scottsdale began negotiations for a third Consent Decree at NIBW. These negotiations were completed October of 2002 for implementation of the Final NIBW Remedy.

Cleanup Ongoing

As mentioned above, the September 1988 groundwater remedy did not achieve containment or capture of the groundwater contamination. As a result, groundwater contamination in the lower aquifer was migrating to the north and threatening the drinking water supply for the City of Paradise Valley. To keep the groundwater contamination from reaching the Paradise Valley wells, several improvements had to be made to the to the September 1988 remedy. These improvements became known as the “Remedy Enhancements” and were conducted by the PRPs on a voluntary basis.

The Remedy Enhancements include the following actions:
1. Installation of new monitoring wells and two new extraction wells;
2. Connection of an additional extraction well to the Scottsdale Groundwater Treatment Facility;
3. Construction of a second groundwater treatment facility (the Miller Road Treatment Facility) to protect the water supply of Paradise Valley;
4. Implementation of a soil cleanup action at Area 6 using SVE;
5. Groundwater extraction and treatment at Areas 7 and 12; and
6. Modifications to improve treatment efficiency at the Scottsdale Groundwater Treatment Facility.

The completion of construction activities at the site were finalized by EPA on September 28, 2006. In 2013, the NIBW Granular Activated Carbon ( GAC) Treatment Facility was completed adjacent to the Paradise Valley's Miller Road Treatment Facility to control the northern edge of the plume.

Cleanup Results to Date

After adding this Site to the NPL, EPA performed preliminary investigations and determined that no immediate actions were required at the Site. Remedies have been selected and cleanup activities in various stages are currently underway at NIBW.

Documents and Reports

Community Involvement

Public Meetings: General public meetings have been held since the late 1980s. Regular Community Involvement Group (CIG) meetings have been held since approximately 1997 to discuss site activities and community concerns regarding NIBW. A public meeting was held on October 10, 2001 to discuss the remedy selected in the September 2001 ROD Amendment and to provide information to the community on EPA's next steps. The most recent CIG meeting was held on February 9, 2011.